Sol - Gel Prepared Ag-doped La <sub> X </ Sub> Of Sr <sub> 0.10 </ Sub> Of Mno <sub> 3-¦Ä </ Sub> Structure Of The Material, Magnetic And Electrical Transport Properties Of

Since the discovery of colossal magnetoresistance effect (CMR) in perovskite manganites, it has sparked considerable interests in potential applications in magnetic information store and low-field magnetic sensors. Beside the CMR effect, these materials also exhibit intriguing physical properties such as phase separation etc. The further understanding of these properties will definitely stimulate the progress of condensed matter physics. In this thesis, the author discusses two basic issues and gives reasonable explanation.The first issue is that whether vacancies can exist at A site in the perovskite structure. Considering the Rietveld fitted results by two hypothesises about vacancies in the samples of LaxSr0.10MnO3-δ(x=0.60, 0.75) and Mn4+ content dependence of the Curie temperature(Tc), the author concludes that, because of Mn2+ entering into A site of the perovskite structure, the samples synthesized by sol-gel process form an ABO3 structure,in which the ionic ratio of A,B and O site is approximately 1:1:3 and there is less vacancies at A site.The second issue is that whether Ag can enter into the perovskite structure in the sol-gel and heating process. The author synthesizes the samples by doping Ag into the matrix LaxSr0.10MnO3-δ(x=0.60, 0.75) and finds that there are three phases, perovskite phase, metal Ag phase and Mn3O4 phase. Considering the results from energy spectrum analysis for the sample composition and the Rietveld fitted results basing on the hypothesis that there is less A site vacancies in the structure, the author gives a conclusion that part Ag enter into the ABO3 perovskites structure. The dependences of the Curie temperature (Tc), the metallic-semiconducting transition temperature (TMI) and the temperature of MR(TP) on the content of Mn4+ at B site, are similar to those of the typical perovskite La1-xSrxMnO3.